CN101372404B - Method for preparing high-strength alpha type hemihydrate gypsum using desulphurized dihydrate gypsum - Google Patents

Abstract

A method for A method for preparing high-strength alpha-hemihydrate gypsum with desulfurated dihydrate gypsum comprises the following steps: desulfurated dihydrate gypsum in an electric power plant is weighted and is mixed with water to form paste, the concentration of the paste ranges from 10% to 50%; then, a crystalline form modifying agent is added in the paste, and one of the following crystalline form modifying agents, such as butane diacid, sodium succinate or magnesium succinate is adopted; the mixing amount of the modifying agent is 0.05 to 0.08 per thousand of the quantity of the desulfurated dihydrate gypsum; the paste, in which the crystalline form modifying agent is added, is heated to 120 to 160 DEG C, and the heat is preserved for 1 to 4 hours, therefore, alpha-hemihydrate gypsum paste is obtained; the alpha-hemihydrate gypsum paste, the temperature of which is at least 90 DEG C, is treated with centrifugal dewatering or vacuum dewatering under the condition of at least 90 DEG C; and finally, the alpha-hemihydrate gypsum paste is baked in a drying plant with the temperature of 120 to 150 DEG C.

Description

A method for preparing high-strength α-type hemihydrate gypsum from desulfurized dihydrate gypsum

technical field

The invention belongs to the preparation technology of building materials, and in particular relates to a method for preparing high-strength α-type hemihydrate gypsum from flue gas desulfurization gypsum.

Background technique

Desulfurization gypsum is a waste produced during flue gas desulfurization in thermal power plants. If it is not utilized, it will cause secondary pollution to the environment. Desulfurization gypsum is a useful industrial resource, but there is still a lack of effective comprehensive utilization at present. The full use of desulfurized gypsum has comprehensive effects such as energy saving and environmental protection. The energy consumption of gypsum production is 1/3 of that of lime and 1/4 of that of cement. Fireproof, it is the best green, energy saving, environmental protection and healthy wall material.

Domestic desulfurization gypsum mainly produces β-type hemihydrate gypsum (ie construction gypsum), with dry compressive strength below 15MPa. So far, no reports and patented technologies have been found to produce high-strength α-type hemihydrate high-strength gypsum with desulfurization gypsum.

Contents of the invention

The invention provides a method for preparing α-type hemihydrate gypsum by using desulfurized dihydrate gypsum. The method can make the prepared α-type hemihydrate gypsum have the advantage of high compressive strength.

The present invention adopts following technical scheme:

A method for preparing α-type hemihydrate gypsum with desulfurized dihydrate gypsum:

Step 1: Take the desulfurized dihydrate gypsum from the power plant, mix the desulfurized dihydrate gypsum from the power plant with water to form a slurry, and the concentration of the slurry is between 10% and 50%, and then add a crystal form modifier to the slurry. The crystal form modifying agent adopts one of the following crystal form modifying agents:

① The crystal form modifier is succinic acid, sodium succinate or magnesium succinate, and the dosage is 0.5‰～8‰ of the mass of desulfurized dihydrate gypsum;

② The crystal form modifier is compounded by one of succinic acid, sodium succinate and magnesium succinate and one of magnesium sulfate and aluminum sulfate, the mass ratio of the two before and after is 1:2~5, The dosage of the crystal form modifier is 5‰～10‰ of the mass of desulfurized dihydrate gypsum;

③Crystal form modifier is compounded by malic acid and magnesium sulfate or malic acid and aluminum sulfate. 3‰～10‰ of quality,

Step 2: heating the slurry after adding the crystal form modifier to 120°C-160°C and keeping it warm for 1h-4h to obtain α-type hemihydrate gypsum slurry;

The α-type hemihydrate gypsum slurry with a temperature not lower than 90°C is subjected to centrifugal dehydration or vacuum dehydration at this temperature; finally, it is dried in a drying equipment at 120°C to 150°C to obtain powder without grinding High-strength α-type hemihydrate gypsum.

Compared with the prior art, the present invention mixes a small amount of crystal form modifier, so that the crystal form of α-type hemihydrate gypsum grows toward the desired short columnar direction, so as to improve the compressive strength of hemihydrate gypsum, and make the gypsum hemihydrate obtained by the present invention The hemihydrate gypsum has the advantage of high compressive strength.

Description of drawings

Fig. 1 is the α-type hemihydrate gypsum prepared by the present invention with 0.2% succinic acid as the crystal form modifier, and the crystal micrograph under the 200 times optical microscope.

Fig. 2 is that the present invention takes 0.2% sodium succinate as crystal form modifier

Fig. 3 is a crystal micrograph of α-type hemihydrate gypsum prepared by using (0.1% succinic acid + 0.2% aluminum sulfate) as a crystal shape modifier under a 200 times optical microscope.

Fig. 4 is a crystal micrograph of α-type hemihydrate gypsum prepared by using (0.1% magnesium succinate + 0.5% aluminum sulfate) as a crystal form modifier under a 200-fold optical microscope according to the present invention.

Fig. 5 is a crystal micrograph of α-type hemihydrate gypsum prepared with 0.25% malic acid as a crystal form modifier under a 200-fold optical microscope.

Fig. 6 is a crystal micrograph of α-type hemihydrate gypsum prepared with 1.5% aluminum sulfate as a crystal form modifier under a 200-fold optical microscope.

Fig. 7 is a crystal micrograph of α-type hemihydrate gypsum prepared with 0.2% magnesium citrate as a crystal form modifier under a 200 times optical microscope.

Fig. 8 is a crystal micrograph of α-type hemihydrate gypsum prepared by using (0.1% magnesium citrate + 0.5% magnesium sulfate) as the crystal form modifier under a 200 times optical microscope.

Fig. 9 is a crystal micrograph of α-type hemihydrate gypsum prepared by using (0.2% sodium citrate + 0.5% aluminum sulfate) as the crystal form modifier under a 200 times optical microscope according to the present invention.

Detailed ways

Example 1:

A method for preparing high-strength α-type hemihydrate gypsum with desulfurized dihydrate gypsum:

Step 1: Take the desulfurized dihydrate gypsum from the power plant, and mix the desulfurized dihydrate gypsum from the power plant with water to form a slurry. The slurry concentration is between 10% and 50%. In this embodiment, the slurry concentration is 10%. 50%, 17%, 32% or 45%, and then add a crystal form modifier to the slurry, and the crystal form modifier adopts one of the following crystal form modifiers:

①The crystal form modifier is succinic acid, sodium succinate or magnesium succinate, the dosage is 0.5‰～8‰ of the mass of desulfurized dihydrate gypsum, for example: the dosage is 0.5‰, 8‰ of the mass of desulfurized dihydrate gypsum , 0.9‰, 3‰ or 7‰;

②The crystal form modifier is compounded by one of succinic acid, sodium succinate and magnesium succinate and one of magnesium sulfate and aluminum sulfate, and the mass ratio of the two before and after is 1:2～5( 1:2, 1:5, 1:3.2 or 1:4.5 can be selected), the dosage of the crystal form modifier is 5‰～10‰ of the quality of desulfurized dihydrate gypsum, in this embodiment, the crystal form modifier The dosage is 5‰, 10‰, 6.7‰, 8‰ or 9‰ of the quality of desulfurized dihydrate gypsum;

③Crystal form modifier is compounded by malic acid and magnesium sulfate or malic acid and aluminum sulfate. 3‰～10‰ of mass, in this embodiment, the dosage of malic acid is 1‰, 6‰, 2.3‰, 4‰ or 5.8‰ of the quality of desulfurized dihydrate gypsum, and the dosage of magnesium sulfate or aluminum sulfate is desulfurized dihydrate gypsum 3‰, 10‰, 5‰, 7.9‰ or 9‰ of the quality of water gypsum;

Step 2: Heat the slurry after adding the crystal form modifier to 120°C-160°C and keep it warm for 1h-4h (for example: heat the slurry to 120°C and keep it for 4h, heat the slurry to 145°C and keep it for 2.4h, or Heating to 160°C and keeping it warm for 1h) to obtain α-type hemihydrate gypsum slurry;

The α-type hemihydrate gypsum slurry with a temperature not lower than 90°C is subjected to centrifugal dehydration or vacuum dehydration at this temperature; finally, it is dried in a drying equipment at 120°C to 150°C to obtain powder without grinding High-strength α-type hemihydrate gypsum.

The rotational speed of the above-mentioned centrifugal dehydration can be 2500 rpm, 3000 rpm or 3600 rpm; the vacuum degree of vacuum dehydration is 450 mmHg, 500 mmHg or 650 mmHg, and the centrifugal or vacuum dehydration temperature is 90 ° C ~ 120 ° C, which can be specifically selected as 90 °C, 105 °C or 120 °C.

Example 2

Main technological scheme of the present invention is:

① First, the power plant desulfurization dihydrate gypsum raw material, crystal form modifier and water are metered and prepared into a slurry with a certain concentration, and pumped into an externally heated autoclave with a slurry pump, and at the same time start the agitator and open the steam valve to heat the autoclave heat up.

②When the temperature of the autoclave rises to about 105°C, open the vent valve to discharge the air, continue to heat up to the required temperature, and keep it for the set time.

③ After the constant temperature is over, open the vent valve to release the air, and when the pressure in the autoclave drops to less than 0.1MPa, put the α-hemihydrate gypsum slurry in the autoclave into the thermal insulation storage tank for standby.

④ According to the requirements of the production speed, put the slurry in the thermal insulation storage tank into a centrifuge (or vacuum dehydrator) for dehydration, and immediately dry it.

The high-strength alpha-type desulfurized hemihydrate gypsum prepared by the invention. Examples of materials and properties of the prepared α-type hemihydrate gypsum are listed in Table 1 and Figures 1-9.

Table 1 Preparation and properties of α-type hemihydrate gypsum

serial number Crystal modifier (mass ‰) Slurry Concentration (%) Constant temperature (℃) Dry compressive strength (MPa) Crystal form 1 Succinic acid 2 40 145 40.1 Figure 1 short columnar 2 Sodium succinate 2 30 145 48.5 Figure 2 Hexagonal granular 3 Succinic acid 1+ Aluminum sulfate 2 30 145 60.7 Figure 3 short column 4 Magnesium succinate 1+ Aluminum sulfate 5 30 145 54.4 Figure 4 short columnar 5 Malic acid 2.5 20 150 40.5 Figure 5 short columnar 6 Magnesium Citrate 2 20 150 15.6 Figure 6 long stick 7 Magnesium Citrate 1 + Magnesium Sulfate 5 30 140 18.5 Figure 7 Acicular 8 Sodium Citrate 2 + Aluminum Sulfate 5 30 140 11.3 Figure 8 Acicular 9 No crystal modifier 20 145 10.4 Figure 9 Fibrous

Analysis of results:

The present invention adopts the α-type hemihydrate gypsum prepared by power plant desulfurization dihydrate gypsum raw material, and the results are listed in Table 1. In order to facilitate the investigation of the change of the α-hemihydrate gypsum crystal form under the action of various crystal form modifiers, a 200 times optical microscope is used to analyze the α-hemihydrate gypsum. They observed and took pictures, and the results are listed in Table 1 and Figures 1-9. The performance of each group of α-hemihydrate gypsum in the comparative example is analyzed as follows by table 1 and Fig. 1～Fig. 9:

1. When no crystal modifier is added (Figure 9), the crystal form of α-type hemihydrate gypsum is fibrous, and the compressive strength is low, only 10.4MPa;

2. When citric acid (salt) is single-doped or mixed with magnesium sulfate and aluminum sulfate as a crystal shape modifier (Figure 6, Figure 7, Figure 8), the effect of crystal transformation is not good, and the crystal shape is generally needle-like or long rod-like ;The compressive strength is low, within 20MPa;

3. Using succinic acid and malic acid as crystal shape modifiers, the high-strength α-type hemihydrate gypsum prepared is short columnar (Figure 1, Figure 5) with high compressive strength, respectively 40.0MPa and 40.5MPa;

4. Using sodium succinate as a crystal form modifier, the high-strength α-type hemihydrate gypsum prepared is hexagonal granular (Figure 2), with a high compressive strength of 48.5 MPa;

5. Using succinic acid and aluminum sulfate, magnesium succinate and aluminum sulfate as crystal shape modifiers, the high-strength α-hemihydrate gypsum prepared is short columnar (Figure 3, Figure 4), and the compressive strength is very high, 55.4MPa and 60.7MPa;

A large number of tests show that, under the process parameter conditions of the present invention, when adopting succinic acid (salt) single-doping or double-doping with aluminum sulfate (magnesium), malic acid and aluminum sulfate single-doping or double-doping, the crystal form is short columnar or Hexagonal granular, can obtain high compressive strength. The crystal form is short columnar, and the hexagonal granular shape is a necessary condition for obtaining high compressive strength.

The invention utilizes the desulfurization dihydrate gypsum waste discharged during the desulfurization of thermal power plants to prepare high-strength α-type hemihydrate gypsum, which can be applied to wall gypsum thermal insulation mortar, light wall gypsum thermal insulation block, gypsum board and architectural gypsum decorative products.

Claims (1)

1. one kind prepares the method for high-strength alpha-type semi-hydrated gypsum with the desulfurization dihydrate gypsum, it is characterized in that:

Step 1: power taking factory desulfurization dihydrate gypsum, and the power plant desulfurization dihydrate gypsum mixed with water form slip, this pulp density adds the crystalline form modifying agent again in slip between 10%～50%, and described crystalline form modifying agent adopts one of following crystalline form modifying agent:

1. the crystalline form modifying agent is Succinic Acid, Soduxin or Succinic Acid magnesium, and volume is 0.5 ‰～8 ‰ of a desulfurization dihydrate gypsum quality;

2. the crystalline form modifying agent is by a kind of and sal epsom in Succinic Acid, Soduxin and the Succinic Acid magnesium and a kind of composite the forming in the Tai-Ace S 150, and both mass ratioes of front and back are 1: 2～5, and the volume of described crystalline form modifying agent is 5 ‰～10 ‰ of a desulfurization dihydrate gypsum quality;

3. the crystalline form modifying agent is by oxysuccinic acid and sal epsom or oxysuccinic acid and Tai-Ace S 150 is composite forms, and the oxysuccinic acid volume is 1 ‰～6 ‰ of a desulfurization dihydrate gypsum quality, and sal epsom or Tai-Ace S 150 volume are 3 ‰～10 ‰ of desulfurization dihydrate gypsum quality;

Step 2: will add slip behind the crystalline form modifying agent and be heated to 120 ℃～160 ℃ and be incubated 1h～4h, and obtain the alpha semi-hydrated gypsum slip;

The alpha semi-hydrated gypsum slip that temperature is not less than 90 ℃ carries out centrifuge dehydration or vacuum hydro-extraction under the condition of this temperature; At last, in 120 ℃～150 ℃ drying plant, dry, promptly obtain the powdered high-strength alpha-type semi-hydrated gypsum.

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